Amyotrophic lateral sclerosis (ALS), also known as Lou Gehrig's disease, is a fatal neurodegenerative disease that poses a significant burden for affected individuals and their family members. The principal objective of this epidemiologic study is to identify environmental and genetic risk factors for ALS. Of primary interest is whether environmental chemicals such as heavy metals, pesticides and organic solvents contribute to the cause of ALS. We also aim to identify genetic factors that contribute to the risk of ALS because individuals with certain genetic traits may be unable to protect against the toxic effects of chemical exposure. Other factors that may protect against the development of ALS, such as dietary antioxidants, are also under investigation. If modifiable factors affecting the risk for ALS could be identified, interventions to delay or even prevent the development of ALS could be developed.